A lens including a lens portion having two opposite oblong lens surfaces, and two flange portions provided at both ends in a direction of a length of the lens portion is known in the art. Each flange portion of this lens tapers toward the lens portion and has a slant surface which slants with respect to the direction of the length of the lens portion and is connected with one of the oblong surfaces. More specifically, the slant surfaces of the two flange portions slant at the same angle, particularly, a steep angle approximate to the right angle, with respect to the direction of the length of the lens portion.
However, such steeply angled flange portions designed to protrude in a direction almost perpendicular to the direction of the length of the lens portion would be disadvantageous in that a cavity surface of a mold contoured to correspond to each slant surface could possibly become obstructive, during manufacture of the lens, to the flow of resin material injected from a gate of the mold formed at a position of the cavity corresponding to an outer end of one flange portion facing outward in a direction of a length of the flange portion. This would make it difficult to mold the lens surfaces precisely.
There is a need to provide a lens and a method for manufacturing a lens which can contribute to the improved flowability of resin or other material during manufacture of the lens.